Electric incandescent lamp and similar device



Jan. 24, 1939. J. AlscH ET AL 2,145,105

ELECTRIC INCANDESCENT LAMP AND SIMILAR DEVICE Filed April 27, 1937Inventors: Johannes Aiscln,

Heinrich Asmus en,

Their Attorney.

Patented Jan. 24,1939

UNITED STATES ELECTRIC INCANDESCENT LAMP AND SIIHILAR DEVICE JohannesAisch,- Falkensee, near Berlin, and Heinrich Asmussen, Bci-lin-Steglitz,Germany, assignors to General Electric Company, a corporation of NewYork Application April 27, 1937, Serial No. 139,290

Germany May 5,

2 Claims. (01. 176-38) Our invention relates to electric. incandescentlamps and similar devices comprising a sealed envelope containing anelectric energy translation element. More particularly our inventionrelates to such devices provided with one or more fuses for preventingthe formation of arcs.

In gas-filled electric lamps, particularly those having double ormultiple coiled tungsten filaments, there is the possibility of theformation w of an arc within the envelope upon breakage of the filamentwith the resulting rise in current which may cause rupturing of the mainline fuse thereby causing all the lamps connected in the same circuit tobe extinguished. In order to avoid this, such gas-filled incandescentlamps have heretofore been equipped with fuses to limit the current. Thesaid fuses are generally in the form of a very thin wire of, forexample, a nickel alloy, which is incorporated in one or more of 20 theleading-in wires. In one such construction a portion of a lead wirebetween the envelope and the base terminal constitutes a fuse. When thisfuse melts a small arc is frequently formed within the base and this aremay lead to explo- 25 sions if the lamp is located in a gaseousatmosphere such as in mines or factories, since the gas enters the basewhich is not hermetically sealed.

According to this invention, the'above-men- 3o tioned disadvantages areobviated by surrounding the fuse with a tube of vitreous material suchas glass which is sealed preferably by fusion at both ends to the leadwire to form a hermetically sealed enclosure for the fuse. With such anarrangement a high gas and vapor pressure is formed within the tube atthe instant that the fuse wire is ruptured. This high gas and vaporpressure is produced by the intense heating of the air and also from theevaporation of the fuse 40 wire. Generally the high gas and vaporpressure entirely prevents the formation of an arc within the vitreoustube, but in any case the arc is extinguished immediately upon itsformation thereby eliminating the danger of an explosion of the 45 gaseswhich have penetrated into the base from the space surrounding the lamp.

It has been suggested heretofore to cover the fuse within the base withan insulating coating of zirconium silicate, or to embody it in thesolidified basing cement which serves as an insulator. Such materials,however, are somewhat porous and therefore do not entirely eliminate thedanger of explosions. There is also danger of the said coatings beingfractured upon rup- 55 turing of the fuse.

Other features and advantages of this invention will appear from thedetailed description thereof and from the drawing.

The drawing is an elevation broadly in section of an incandescent lampcomprising my invention.

Referring to the drawing, the lamp comprises a glass bulb I which isfilled with an inert gas or gases such as a mixture of argon andnitrogen or, carbon and nitrogen. The lamp is provided with the usualmount comprising a stem tube 2, arbor 3 and exhaust tube 4. The ends ofthe coiled coil filament 6, which is supported on support wires 5, areattached to the inner ends of lead wires 1, I which are in turn securedto the press leads 9, 9' which are sealed in the stem press 8. Two thinwires l0, H) of an alloy having a low melting point, such as a nickelalloy, are secured to the opposite ends of the said press leads 9, 9'.The said thin wires l0, Ill constitute the fuses for the'lamp. The outerends of u said wires III, III are connected to the base shell l2 and endcontact l3 by means of wires H, II

of copper, for example. Glass tubes M, It surround the said fuse wiresIll, Ill and have their ends sealed by fusion to the adjacent ends ofthe wires 9, 9' and H, II' so that the said fuse wires are whollyenclosed in the said tubes l4, l4 and are surrounded by a relativelysmall quantity of enclosed air.

The invention may of course be used in various types of lamps such astungsten arc lamps, vapor discharge lamps and photofiash lamps, and alsofor discharge tubes, high capacity rectifiers and X-ray tubes. Insteadof incorporating a fuse in each of the lead wires, it is of coursepossible to incorporate a fuse in only one of the said wires, or whenthere are more than two lead wires, to employ fuses in only a few ofthem. Each fuse may consist of a thin metal strip having a low meltingpoint instead of being made of thin wire.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. An electrical device comprising a. sealed envelope, a base on saidenvelope, an electric energy translation element in said envelope, leadwires 5 extending through said envelope and electrically connected tosaid translation element, the outer ends of said lead wires extending toterminals on said base, a portion of at least one of said lead wiresbetween said envelope and said base constituting a fuse, and a tube ofvitreous material surrounding said fuse and sealed by fusion at bothends to said lead wire at points beyond the ends of said fuse portion tohermetically enclose said fuse. u

between said envelope and said base constituting a fuse. and a tube ofvitreous material surroundmg each of said fuses and sealed by fusion atboth ends to the lead wire surrounded thereby at points beyond the endsof the fuse portion to hermetically enclose said fuses.

J OHANNES AISCH. HEINRICH ASMUSSEN.

